打印所有行：（$0代表整条记录）
awk '{print $0}' employee.txt awk '{print}' employee.txt
上面两条命令等价，都是打印employee.txt所有行。
输入字段分隔符：
- 使用FS代表输入字段分隔符
- 如果只有body部分，只用F即可，如果有不同的分隔符间隔，就需要使用FS了
- FS分隔符只能在BEGIN中使用
举例：
cat employee-multiple-fs.txt 101,John Doe:CEO%10000
awk 'BEGIN{FS="[,:%]"}{print $2,","$3}' employee-multiple-fs.txt
John Doe ,CEO
cat employee.txt 101,John Doe,CEO
awk -F "," '{print $2,","$3}' employee.txt
John Doe ,CEO
输出字段分隔符：
- 使用OFS作为输出字段分隔符
- 如果不使用OFS，awk会默认以空格方式分割
- OFS也是在BEGIN中使用的
举例：
cat employee.txt 101,John Doe,CEO
awk -F "," '{print $2,":",$3}' employee.txt
John Doe : CEO
cat employee.txt 101,John Doe,CEO
awk -F "," 'BEGIN{OFS=":"}{print $2,$3}' employee.txt
John Doe:CEO
记录分隔符：
- 使用RS代表记录分隔符，即人为的将多条记录分成一行行的
举例：
cat employee-change-fs-ofs.txt 101 John Doe CEO - 102 Jason Smith IT Manager - 103 Raj Reddy Sysadmin - 104 Anand Ram Developer - 105 Jane Miller Sales Manager
打印雇员名称和职位：
awk 'BEGIN{RS="- ";FS=" ";OFS=":"}{print $2,$3}' employee-change-fs-ofs.txt
John Doe:CEO
Jason Smith:IT Manager
Raj Reddy:Sysadmin
Anand Ram:Developer
Jane Miller:Sales Manager
输出记录分隔符：
- 使用ORS代表输出记录分隔符，用来输出一行一行的分隔符
举例：
cat employee-change-fs-ofs.txt 101 John Doe CEO - 102 Jason Smith IT Manager - 103 Raj Reddy Sysadmin - 104 Anand Ram Developer - 105 Jane Miller Sales Manager
awk 'BEGIN{RS="- ";FS=" ";OFS=":";ORS=" ------ "}{print $2,$3}' employee-change-fs-ofs.txt
John Doe:CEO ------ Jason Smith:IT Manager ------ Raj Reddy:Sysadmin ------ Anand Ram:Developer ------ Jane Miller:Sales Manager ------
记录序号：
- 用NR代表记录序号
- 用于统计当前记录在所有记录中的行号
- 末尾处可以表示总行数，即：在END区域时，代表输入文件的总记录数
举例：
cat employee.txt 101,John Doe,CEO 102,Jason Smith,IT Manager 103,Raj Reddy,Sysadmin 104,Anand Ram,Developer 105,Jane Miller,Sales Manager
awk 'BEGIN{FS=","}{print "Emp id of record number",NR,"is",$1}END{print "Total number of records:",NR}' employee.txt
Emp id of record number 1 is 101 Emp id of record number 2 is 102 Emp id of record number 3 is 103 Emp id of record number 4 is 104 Emp id of record number 5 is 105 Total number of records: 5
- 当NR在awk中有多个输入文件时，NR不会被重置为1，而是在前一个文件的NR基础上继续增加
举例：
cat employee.txt 101,John Doe,CEO 102,Jason Smith,IT Manager 103,Raj Reddy,Sysadmin 104,Anand Ram,Developer 105,Jane Miller,Sales Manager cat employee-multiple-fs.txt 101,John Doe:CEO%10000 102,Jason Smith:IT Manager%5000 103,Raj Reddy:Sysadmin%4500 104,Anand Ram:Developer%4500 105,Jane Miller:Sales Manager%3000
awk 'BEGIN{FS=","}{print FILENAME": record number",NR,"is",$1}END{print "Total number of records:",NR}' employee.txt employee-multiple-fs.txt
employee.txt: record number 1 is 101 employee.txt: record number 2 is 102 employee.txt: record number 3 is 103 employee.txt: record number 4 is 104 employee.txt: record number 5 is 105 employee-multiple-fs.txt: record number 6 is 101 employee-multiple-fs.txt: record number 7 is 102 employee-multiple-fs.txt: record number 8 is 103 employee-multiple-fs.txt: record number 9 is 104 employee-multiple-fs.txt: record number 10 is 105 Total number of records: 10
- FNR与NR的区别：同时有多个输入文件时，NR不会重置，会一直累加；而FNR会重置
举例：
cat employee.txt 101,John Doe,CEO 102,Jason Smith,IT Manager 103,Raj Reddy,Sysadmin 104,Anand Ram,Developer 105,Jane Miller,Sales Manager cat employee-multiple-fs.txt 101,John Doe:CEO%10000 102,Jason Smith:IT Manager%5000 103,Raj Reddy:Sysadmin%4500 104,Anand Ram:Developer%4500 105,Jane Miller:Sales Manager%3000
awk 'BEGIN{FS=","}{print "FILENAME="FILENAME,"NR="NR,"FNR="FNR}END{print "END Block:NR="NR,"FNR="FNR}' employee.txt employee-multiple-fs.txt
FILENAME=employee.txt NR=1 FNR=1 FILENAME=employee.txt NR=2 FNR=2 FILENAME=employee.txt NR=3 FNR=3 FILENAME=employee.txt NR=4 FNR=4 FILENAME=employee.txt NR=5 FNR=5 FILENAME=employee-multiple-fs.txt NR=6 FNR=1 FILENAME=employee-multiple-fs.txt NR=7 FNR=2 FILENAME=employee-multiple-fs.txt NR=8 FNR=3 FILENAME=employee-multiple-fs.txt NR=9 FNR=4 FILENAME=employee-multiple-fs.txt NR=10 FNR=5 END Block:NR=10 FNR=5
打印偶数行：
cat items.txt 101,HD Camcorder,Video,210,10 102,Refrigerator,Appliance,850,2 103,MP3 Player,Audio,270,15 104,Tennis Racket,Sports,190,20 105,Laser Printer,Office,475,5
awk 'NR%2 ==0' items.txt
102,Refrigerator,Appliance,850,2 104,Tennis Racket,Sports,190,20
在awk中调用文件执行命令：
cat fnr.awk BEGIN{FS=","}{print "FILENAME="FILENAME,"NR="NR,"FNR="FNR}END{print "END Block:NR="NR,"FNR="FNR}
执行awk命令：
awk -f fnr.awk employee.txt employee-multiple-fs.txt
FILENAME=employee.txt NR=1 FNR=1 FILENAME=employee.txt NR=2 FNR=2 FILENAME=employee.txt NR=3 FNR=3 FILENAME=employee.txt NR=4 FNR=4 FILENAME=employee.txt NR=5 FNR=5 FILENAME=employee-multiple-fs.txt NR=6 FNR=1 FILENAME=employee-multiple-fs.txt NR=7 FNR=2 FILENAME=employee-multiple-fs.txt NR=8 FNR=3 FILENAME=employee-multiple-fs.txt NR=9 FNR=4 FILENAME=employee-multiple-fs.txt NR=10 FNR=5 END Block:NR=10 FNR=5
在sed中调用文件执行命令：
cat mycommands.sed #!/bin/sed -f #交换第一列与第二列 s/([^,]*),([^,]*),(.*).*/2,1,3/g #把整行内容放入<>中 s/^.*/<&>/ #把Developer替换为IT Manager s/Developer/IT Manager/ #把Manager替换为Director s/Manager/Director/
执行sed命令：
cat files.txt /etc/passwd /etc/group
./mycommands.sed files.txt
</etc/passwd>
</etc/group>
执行sed命令与awk命令的区别：
- sed文件需要写上#!/bin/sed -f ，而awk文件只需要写awk ' '引号中的内容
- 注意：awk文件不能写引号
- 执行sed文件前要给.sed文件赋权限，而awk文件需要使用命令-f调用.awk文件
getline命令：
awk在开始执行body区域时，执行任何命令之前，都会从文件中先读取一行数据，保存在变量$0中，然后再执行body中的内容。
比如：
awk -F"," '{getline tmp; print $0;}' items.txt
cat items.txt 101,HD Camcorder,Video,210,10 102,Refrigerator,Appliance,850,2 103,MP3 Player,Audio,270,15 104,Tennis Racket,Sports,190,20 105,Laser Printer,Office,475,5
结果为：
101,HD Camcorder,Video,210,10 103,MP3 Player,Audio,270,15 105,Laser Printer,Office,475,5
只打印奇数行内容。getline tmp强制awk读取下一行，并保存在变量$0中，print $0时，$0仍然是第一行数据，因为getline tmp没有覆盖$0，因此会打印第一行数据，而不是第二行。body区域继续执行，只打印奇数行的数据。